Many structures in the colder climates face water damage due to the build up of ice dams on their roofs during the winter months. Snow builds up on the roof and creates an insulating layer between the outside environment and the roof. As residual heat escapes from the structure through the roof, the snow in the proximity of the roof begins to melt and the water runs down the roof under the snow as is the case in a rain storm. Normally, this water leaves the roof by passing over the eave and off the roof.
Under certain cold conditions, the roof areas above the eaves become cold because they are not heated by the residual heat escaping from the structure. The water then freezes as it contacts the cold roof area over the eaves. This in turn causes ice to build up on the roof over the eaves, which in turn forms a barricade or an ice dam. The water behind the dam and on the roof remains in a liquid form due to the residual heat escaping from the structure. Pitched shingled roofs are constructed from overlapping shingles, therefore the standing water behind the dam may seep under the shingles and into the structure causing water damage.
Most overlaid shingled roofs are not designed to seal against the standing water caused by ice dams. They are designed, through their overlaid placement, to seal against water running off the roof. When water stands on a pitched shingled roof, the water seeps under the shingles, through the roof substrate and into the structure.
There are construction methods used to protect structures from damage caused by water standing on their pitched shingled roofs. These include placing low friction roof elements on the eaves, so the ice slides off the roof. Some systems use electric heaters placed upon the eaves to melt the ice dams or to keep them from forming. Another way to prevent water damage to the structure is by placing a waterproof membrane on the substrate and under the shingles. In the event an ice dam occurs the membrane seals the structure from the standing water preventing water from contacting the substrate.
When an existing roof leaks due to ice dams, the method to fix it is rather extensive. The shingles are stripped from the roof so that a membrane may be placed upon the substrate. The membrane generally used is an adhesive membrane that adheres to the substrate. The industry standard is a 0.040" waterproof membrane. The membrane is adhered to the substrate and the shingles are laid, in overlapping fashion, on the membrane. They are then affixed to the substrate. This requires disposing roofing shingles that themselves may be functional and placing new shingles on the roof.
A problem exists in many colder climates because many structures were constructed without any ice dam prevention measures or measures to prevent damages caused by standing water on the roofs. This problem was not noticed for several years in many of the northern areas because the conditions had not been right to form ice dams for several years. Recently, ice dams have formed and these structures have suffered considerable damage as a result of water leaking through their roofs and into the structures.
This problem has been compounded in larger structures such as condominiums. Many of the condominiums are fairly large structures that were built economically. In some cases, the trusses flex slightly, which in turn causes the shingles to crack. The stressing may also cause the flashing to leak due to being misplaced or due to the adhesion on the flashing becoming undone. The roof then leaks more often and the volume of leaking water in the case of an ice dam increases.
The only way to solve the ice dam problem on many of these structures is by placing a waterproof membrane upon the roof. The methods used to date consist of placing the membrane directly on the roof substrate and under the roofing shingles as set forth above. This requires removing the existing roofing shingles, placing the membrane on the substrate and then placing new roofing shingles on the membrane. The reason for removing the existing roof is that none of the membrane or shingle manufacturers have found a suitable method for placing a second membrane on the existing shingles and placing the new roofing shingles on the second membrane. The membrane must be compatible with flashing components, otherwise, the standing water may seep around their junction, through vertical roof components and into the structure. The membrane must also be strong enough to withstand the forces exerted through the shingles. The shingles do not lay flat, so stress is created; should the membrane tear under the stress, the roof will be susceptible to ice dam damage.
An additional problem exists with disposing of asphalt roofing shingles. Stripping a roof creates an enormous amount of waste that may be considered hazardous or require special disposal techniques given the municipality. Stripping a roof to replace or install a membrane creates the waste disposal problem. In addition, if the first membrane is adhered to the substrate, replacing the roof may damage an otherwise good substrate. Therefore, there exists a need for a method to waterproof roofs against standing water without stripping the existing shingles and without causing damage to the substrate.
The applicant has found a membrane that can be used on a first layer of existing roofing shingles and under a new layer of shingles. This allows the new roofing shingles to be replaced without the expense of removing the existing shingles. This procedure saves on the cost of replacing the roof. At present, the applicant has found that many roofs are leaking after about ten years when in fact they should be lasting for about thirty years. After thirty years, most people expect to place a second layer of shingles on the first layer and completely strip the roof after a total of sixty years. This method of roofing saves the first layer of shingles, so the roof should not need to be stripped for approximately forty years from the date it was first installed. Further, the applicant has found that the membrane may be placed over existing flashing to assure a waterproof roof without the cost of replacing existing flashing. The membrane is durable enough to withstand the aforementioned stresses in the roof and by movement of the trusses.